Aqua Ultraviolet Ultima II Filters utlize "cyclonic" backwashing to ensure easy cleaning of filter media and optimal water quality. These professional-grade bead filter systems are well-known for low maintenance, high performance, and reliability. Aqua Ultima II filters are packed with ultra-high filtration bio-media that provides both mechanical and biological filtration, ideal for aquariums and fish ponds. The advantage of the Ultima II filter is it's non-organic filter media with properties that encourage bacteria growth. Research led to three different types of media designed to grow and hold ammonia oxidizing bacteria and heterotrophic bacteria. Just one cubic foot of these three media has over two million tiny shapes. One cubic foot of Ultima II media is equal to 750 square feet of surface area. Cleaning is done by internal jets backwashing.